The invention relates to a colour television display tube comprising a glass envelope having a display window, a cone and a neck, the outer surface of the cone having a number of abutments for positioning a system of deflection coils on the envelope of the tube.
Such a colour display tube is known from the article "30 AX-Self aligning 110.degree. in line colour T.V. display" in I.E.E.E. Transactions on Consumers Electronics, Vol. CE-24, No. 3, August, 1978. pp. 481-7. In the colour display tube described in said article the cone comprises three abutments in the form of studs to position the system of deflection coils on the envelope of the tube. The system of deflection coils has three abutments which cooperate with the three studs on the cone. The system of deflection coils further comprises a clamping ring which surrounds the neck of the tube and with which the system of deflection coils is fixed, after it has been slid on the tube until the abutments of the system of deflection coils bear against the studs on the cone. The studs on the cone have a given thickness for each tube, which thickness is chosen so that tolerance in the manufacture of the tube are compensated. These studs, which adhere to the cone, are manufactured from a non-ferromagnetic material.
The studs must satisfy a number of stringent requirements. It must be possible to attach them to the glass surface of the cone in a readily adhering manner for a long period of time. Their dimensions must be accurately reproducible and it must be possible to manufacture them in a simple manner with the desired dimensions to minimize the cost of production of the display tube.